1. Field of the Invention
The present invention relates to catalytic reaction method and apparatus for utilizing thermal energy generated by chemical reactions using catalysts.
2. Description of Related Art
Catalytic reaction apparatuses having catalytic reaction tubes have been used after they were filled with catalysts uniformly and heat or thermal energy generated by the reaction in the reaction tube has been taken out with a heat collecting medium arranged outside the reaction tube as will be described below with reference to FIGS. 1 and 2. FIG. 1 is a schematic Cross-sectional view showing a conventional catalytic reaction tube in a catalytic reaction apparatus. FIG. 2 is a graph illustrating distribution of temperature in the conventional catalytic reaction tube. In FIG. 1, reference numeral 10 designates a catalytic reaction tube for carrying out a catalytic reaction, 12 is an inlet side of the catalytic reaction tube 10, and 14 is an outlet side of the catalytic reaction tube 10. A and B designate first and second raw materials for the reaction, C and D designates first and second products produced by the reaction, X is a catalyst, F is a heat medium, and Q indicates reaction heat generated by the reaction.
As shown in FIG. 1, the catalyst X is arranged or distributed uniformly in the catalytic reaction tube 10. At the inlet side 12 of the catalytic reaction tube, the first and second raw materials A and B are introduced and brought in contact with the catalyst X to produce the first and second products C and D, for example, which are outputted at the outlet side 14 of the catalytic reaction tube 10. The catalytic reaction generates reaction heat, which transmits through a wall 16 of the catalytic reaction tube 10 to the heat medium F. The heat medium F flows along the wall 16 of the catalytic reaction tube 10 in the direction from the inlet side 12 toward outlet side 14, that is, concurrently with the flow of the raw materials A and B. In the above-described conventional method, there appears a localized high temperature region inside the catalytic reaction tube 10 as shown in FIG. 2. More particularly, in the conventional catalytic reaction tube 10, which is filled with the catalyst X uniformly, the raw materials A and B react with each other while they are flowing through the catalytic reaction tube. An increasing amount of heat generates or the inside temperature increases according as the position Px along an axis of the catalytic reaction tube 10 approaches from the position Pi at the inlet to the position Po at the outlet of the catalytic reaction tube 10 up to a certain position Pm. Beyond the position PM, heat generation decreases due to a decrease in the amounts of unreacted raw materials so that the loss of heat by transmission exceeds the heat generation by the chemical reaction. In this manner, there appears a peak in a curve 18. In accordance with this change in the inner temperature of the chemical reaction tube 10, the temperature of the heat medium F changes as represented by a curve 19.
Therefore, when heat is taken out with the heat medium F by the conventional method, the outlet temperature of the heat medium F depends on the temperature at the outlet side 14 of the catalytic reaction tube 10 and, hence, it is impossible to supply heat to the external system at a temperature exceeding that of the outlet side 14 of the catalytic reaction tube 10. Therefore, the reaction heat generated inside the catalytic reaction tube 10 has not always been utilized efficiently.
As described above, with the method and apparatus using the conventional catalytic reaction tube 10 that is filled with a catalyst uniformly, not only the inner temperature of the tube 10 locally increases so that the reaction conditions vary locally but also the reaction temperature at the outlet side 14 of the reaction tube 10 is lower than that of the heat medium F. Therefore, no efficient heat exchange with the external system. Furthermore, there is a problem that such a local temperature increase results in the production of undesired by-products.